Contemporary coronary bypass surgery commonly entails grafting a segment of a patient's own blood vessel around a stenosis or other anomaly in a coronary artery to improve circulation in regions of the cardiac muscle adversely affected by diminished blood flow past such stenosis or anomaly. The bypass or shunting vessel is commonly prepared from the patient's saphenous vein or radial artery, and minimally invasive techniques are now routinely employed to harvest a segment of such vein using subcutaneous surgical instruments and procedures that dissect the saphenous vein from connective tissue to promote convenient harvesting of the vessel with minimal cutaneous incision.
Specifically, common surgical practices for harvesting the saphenous vein include making a small incision over the vein near the knee to expose the vein and facilitate introduction of an elongated tissue dissector to dissect connective tissue from the vein along its course in either or both directions from the incision near the knee. The saphenous vein may thus be separated from surrounding connecting tissue, and the anatomical space or cavity thus formed along the course of the vessel may be maintained open under insufflation of the cavity to facilitate operation on the vein. To implement such maintenance of a working space about the vessel being harvested, an access port with a sliding gas seal may be installed in the initial incision and endoscopic instruments may be passed through the seal and manipulated to harvest the vessel from within the cavity which is expanded by gas supplied thereto under pressure. Lateral or side branches of the vessel may be cauterized or otherwise ligated and transected to free the saphenous vein from anatomical attachments and then severed near extreme ends of the cavity for removal from the body, for example, through the initial incision.
Current systems commonly employ a balloon coupled to the cannula for intermittent inflation and deflation to enlarge the surgical cavity as the cannula is advanced. However, use of a balloon to enlarge surgical cavities has the disadvantage that multiple balloon inflation and deflation tires the surgeon's hands, and makes it difficult to retain the precise hand control needed to perform the surgical procedure.
In such vessel harvesting procedure, it is highly desirable to have visualization of the vessel as tissue is bluntly dissected away from the vessel and around side branches within the cavity, and it is highly desirable to have endoscopic instruments selectively available at the distal end of an elongated device that is manipulable within the insufflated anatomical space through a gas-seal to occlude and sever side branches of the saphenous vein in preparation for harvesting of the vessel from the patient's body. Similarly, it is highly desirable to establish minimally invasive techniques for harvesting a radial artery.
However, harvesting an arterial conduit is more difficult and hazardous than harvesting a venous conduit. Inadvertent transection of an arterial side branch during tissue dissection leads to hemorrhage from the artery, which is under high pressure. The dissection tunnel immediately fills with blood, and prevents visualization of the vessel for further exposure of the artery. If a side branch is stretched and partially avulsed or torn, the high pressure in the artery causes blood to dissect along the medial and adventitial layers of the artery, expanding the wall of the artery like a balloon, and ruining the vessel for use as a graft.